Butyl Hydroperoxide Research Articles

NADPH-dependent peroxidase activity of antibodies in patients with schizophrenia

IntroductionThe development of oxidative stress in patients with schizophrenia is associated with changes in the level of activity of antioxidant enzymes. It is likely that catalytically active antibodies (abzymes) can take on these functions. Abzymes are antibodies with enzymatic activity. Catalase and SOD activity of abzymes was previously detected in patients with schizophrenia. But NADPH-dependent peroxidase activity has not been studied. The present work discusses the protective role of abzymes against reactive oxygen species within the pathogenesis of schizophrenia.ObjectivesThe aim of the study was to investigate the NADPH-dependent peroxidase activity of IgG in patients with paranoid schizophrenia in the exacerbation phase and in the remission phase.MethodsA total of 124 patients were examined during the work. Of them, 82 patients with paranoid schizophrenia (F20.0) had a mean age of 33.6±5.12 years (52 males, 30 females), disease duration averaged 8.9± 4.62 years. Patients with schizophrenia included 42 patients with acute schizophrenia and 40 patients with schizophrenia in therapeutic remission. The control group included 42 sex- and age-matched patients. IgG was purified by affinity chromatography on columns with proteinsepharose on an AKTA purifier chromatograph (GE). The homogeneity of isolated IgG preparations was checked by Lemilly electrophoresis in a gradient of 4-18% PAAG. Gel filtration under pH-shock conditions was performed on a Superdex-200 HR 10/30 column. NADPH-dependent peroxidase activity of IgG was determined on a SPECORD M-40 spectrophotometer (Carl Zeiss) at 340 nm by NADPH oxidation in the conjugated glutathione reductase reaction of tertiary butyl hydroperoxide reduction. Statistical processing of data was performed in Statistica 12.0 program.ResultsIt was proved that IgG from patients with schizophrenia had NADPH-dependent peroxidase activity, and this activity is an intrinsic property of the investigated antibodies. The NADPH-dependent peroxidase activity in IgG patients in the exacerbation stage was increased 3-fold (p=0.0001) compared to the studied activity in the group of healthy individuals, and it was increased 2-fold (p=0.017) in the group of patients in therapeutic remission compared to the activity in healthy individuals. Also NADPH-dependent IgG peroxidase activity in patients in remission was 1.7 times lower than in patients during the exacerbation period (p=0.012).ConclusionsIt was established for the first time that abzymes from patients with schizophrenia and healthy individuals have NADPH-dependent peroxidase activity and can decompose lipo and hydroperoxides. We hypothesize that these abzymes help cope with generalized oxidative stress. Under the influence of neuroleptic therapy in patients in remission, the level of oxidative stress and NADPH-dependent peroxidase activity of abzymes decrease.Disclosure of InterestNone Declared

Insights into the Palladium(II)-Catalyzed Wacker-Type Oxidation of Styrene with Hydrogen Peroxide and tert-Butyl Hydroperoxide.

Wacker oxidations are ubiquitous in the direct synthesis of carbonyl compounds from alkenes. While the reaction mechanism has been widely studied under aerobic conditions, much less is known about such processes promoted with peroxides. Here, we report an exhaustive mechanistic investigation of the Wacker oxidation of styrene using hydrogen peroxide (H2O2) and tert-butyl hydroperoxide (TBHP) as oxidants by combining density functional theory and microkinetic modeling. Our results with H2O2 uncover a previously unreported reaction pathway that involves an intermolecular proton transfer assisted by the counterion [OTf]- present in the reaction media. Furthermore, we show that when TBHP is used as an oxidant instead of H2O2, the reaction mechanism switches to an intramolecular protonation sourced by the HOtBu moiety generated in situ. Importantly, these two mechanisms are predicted to outcompete the 1,2-hydride shift pathway previously proposed in the literature and account for the level of D incorporation in the product observed in labeling experiments with α-d-styrene and D2O2. We envision that these insights will pave the way for the rational design of more efficient catalysts for the industrial production of chemical feedstocks and fine chemicals.

Unravelling the different pathways of cyclohexene oxidation via a peroxyl radical generated from tert-butyl hydroperoxide (TBHP) by various metal salts

Two different mechanisms were obtained in the selective oxidation of cyclohexene catalyzed by CuCl2 and VCl3 respectively in presence of TBHP. The two opposed mechanisms are mainly caused by the roles of the t-BuOO˙ radical in catalytic oxidations.

Синтез и строение бис[3,4-дифторбензоата] трис(2-метоксифенил)сурьмы [(2-MeO)C6H4]3Sb[OC(O)C6H3(F2-3,4)]2 и бис[бензолсульфоната] трис(2-метоксифенил)сурьмы [(2-MeO)C6H4]3Sb[OSO2C6H5

Tris(2-methoxyphenyl)antimony bis[3,4-difluorobenzoate] (1) and tris(2-methoxyphenyl)antimony bis[benzenesulfonate] (2) were obtained by oxidative addition reaction from triarylantimony and 3,4-difluorobenzoic/benzenesulfonic acid in the presence of tertiary bu-tyl hydroperoxide in ether. The structure of 1 and 2 was established with the use of IR spectrosco-py and X-ray diffraction analysis (XRD). Crystals 1 [C35H27O7F4Sb, M 757.32; triclinic syngony, symmetry group P–1; cell parameters: a = 9.219(4), b = 9.507(6), c = 20.240(11) Å; a = 99.43(3)°, β = 95.756(16)°, g = 107.90(3)°; V = 1643.6(16) Å3; Z = 2; rcalc = 1.530 g/cm3; 2q 6.68-54.98 de-grees; total reflections 31858; independent reflections 7153; number of specified parameters 427; Rint = 0.0429; GOOF 1.051; R1 = 0.0265, wR2 = 0.0551; residual electron density (max/min); 0.30/-0.44 e/Å3], 2 [C33H31O9S2Sb, M 757.46; monoclinic system, symmetry group C2/c; cell parame-ters: a = 21.157(9), b = 10.363(4), c = 18.285(7) Å; β = 126.590(13) deg., V = 3219(2) Å3, Z = 1; rcalk = 1.563 g/cm3; 2q 6.012-54.234 degrees; total reflections 32454; independent reflections 3541; number of specified parameters 231; Rint = 0.0283; GOOF 1.161; R1 = 0.0283, wR2 = 0.0659; residual electron density (max/min); 0.74/-0.83 e/Å3] consist of trigonal bipyramidal molecules with electronegative ligands in axial positions. The Sb–C bond lengths vary in the range 2.093(2)−2.125(3) Å, The OSbO bond angles take values 176.63(6)° and 174.52(10)°, respective-ly. The Sb–O distances in 1 (2.1106(17) and 2.1149(17) Å) are shorter than in 2 (2.128(2) and 2.128(2) Å). Intramolecular Sb∙∙∙O contacts in 1 (3.162(2) and 3.257(2) Å) are significantly smaller than in 2 (3.617(2) and 3.617(2) Å) and do not exceed the sum of their van der Waals radii (3.7 Å). Complete tables of atomic coordinates, bond lengths and bond angles for structures have been de-posited in the Cambridge Structural Data Bank (No. 2123247 (1), No. 2116583 (2), depos-it@ccdc.cam.ac.uk; http://www.ccdc cam.ac.uk).

Синтез и строение сольвата бис[3,5-динитробензоата] трис(2-метокси)(5-бром)фенилсурьмы [C6H3(2-OMe)(5-Br)]3Sb[OC(O)C6H3(NO2)2-3,5]2 ∙ PhH ∙ ½ C8H18

Tris(2-methoxy)(5-bromo)phenylantimony bis[3,5-dinitrobenzoate] (1) was obtained from 3,5-dinitrobenzoic acid by oxidative addition to triarylantimony in the presence of tertiary butyl hy-droperoxide in ether, and was isolated by recrystallization from a benzene-octane mixture in the form of a crystal solvate with benzene and octane molecules in its crystal lattice. The structure of solvate 1 was established by the IR spectroscopy and X-ray diffraction analysis (XRD). In the IR spectrum of complex 1, in addition to the absorption bands related to the stretching vibrations of the Sb–C, СAr–О–Ме, and carbonyl groups, there are bands corresponding to the stretching vibra-tions of the C–Br bonds (524 and 555 cm–1). The X-ray diffraction data show that the antimony at-oms in complex 1 have a distorted trigonal bipyramid coordination with carboxylate ligands in the axial position. The antimony atom and two oxygen atoms do not lie on the same straight line and are located in such a way that the OSbO angle is 170.79°. The O…Sb distances (2.134(4) and 2.110(5) Å) are close to the sum of the covalent radii of antimony and oxygen. In addition, accord-ing to the X-ray diffraction data, compound 1 crystallizes in the monoclinic crystal system, space group P21/n. The structural organization in the crystal is formed due to short contacts of oxygen atoms in the nitro groups of the carboxylate ligands with carbon and bromine atoms of the aryl lig-ands of neighboring molecules, as well as hydrogen O...H (2.524–2.715 Å) bonds. In addition, a certain contribution to the formation of the crystal structure is made by the p-p stacking between the aromatic rings of crystallization benzene and the methoxy-bromo-phenyl ligands. The aro-matic rings are displaced in relation to each other and the distance between them is 3.367 Å. Melt-ing point of solvate 1 is 172.6 °C, according to the thermal analysis data. However, further in-crease in temperature is accompanied by decomposition of compound 1, and therefore an exo-thermic peak is observed on the DSC curve at 255.7 °C, corresponding to a mass loss of 31 % ac-cording to the TGA data. Complete tables of atom coordinates, bond lengths, and valence angles are deposited at the Cambridge Crystallographic Data Center (No. 2060562, depos-it@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk/data_request/cif)

Enhancing aerobic oxidation of C–H bonds through efficient catalysis of iron MOF–derived Fe3C nanoparticles embedded in porous carbon catalysts

Developing efficient heterogeneous catalysts for the aerobic oxidation of C–H bonds using oxygen molecule as an oxidant to produce value–added aryl ketones is a challenging task. In this study, a series of cementite–iron–carbon composites (referred to as Fe–C–T, where T represents the pyrolysis temperature) were synthesized using a metal–organic–framework–mediated sacrificial template strategy. The Fe–C–T composites consist of highly dispersed Fe/(Fe3C or Fe2O3) nanoparticles surrounded by graphitic carbon on porous carbon supports. Under mild reaction conditions (1 atm of O2 pressure, 353 K, 12 h), with tert–butyl hydroperoxide (0.25 equiv.) as the initiator in a green solvent water, the prepared Fe–C–973 achieved a high conversion of 98.4 % for ethylbenzene and a selectivity of 98.7 % for acetophenone. This performance was markedly superior to the comparable Fe–C–873 and Fe–C–1073, as well as the commercially available Fe–based catalysts. Kinetic studies revealed that the catalytic system followed first–order kinetics for the substrate ethylbenzene, and the activation energy over Fe–C–973 was remarkably low of 40.4 kJ/mol. The highly distributed Fe3C nanoparticles embedded in the porous carbon framework were identified as the most active sites for the reaction.

Angelica sinensis polysaccharide improves mitochondrial metabolism of osteoarthritis chondrocytes through PPARγ/SOD2/ROS pathways.

Osteoarthritis (OA) is a common degenerative joint disease, which is characterized by wear of articular cartilage and narrow joint space, resulting in joint movement disorder. At present, accurate molecular mechanisms and effective interventions are still being explored. Here, we propose that angelica sinensis polysaccharide (ASP) alleviates OA progression by activating peroxisome proliferator-activated receptor gamma (PPARγ). Therapeutic effect of ASP improving mitochondrial metabolism of OA chondrocytes was evaluated in vitro and in vivo, respectively. During cell experiments, the concentration and time response of tert butyl hydroperoxide (TBHP) and ASP were determined by cell viability. Apoptosis was detected by flow cytometry. Mitochondrial metabolism was detected by reactive oxygen species (ROS), mitochondrial membrane potential (MMP), release of cytochrome C, adenosine triphosphate (ATP) production, and superoxide dismutase 2 (SOD2) activity. Expressions of Aggrecan, collagen type II (Col2a1), PPARγ, and SOD2 were detected by qRT-PCR and western blot. In animal experiments, we detected cell apoptosis and target protein expression separately through terminal deoxynucleotidyl transferase dUTP nick end-labeling (TUNEL) staining and immunohistochemistry. Pretreatment of ASP significantly activated PPARγ and SOD2 in rat chondrocytes incubated with TBHP, cleared ROS, improved mitochondrial metabolism, increased chondrocytes viability, and alleviated chondrocytes apoptosis. In vivo, the administration of ASP could effectively ameliorate cartilage degeneration in OA rats, promote extracellular matrix synthesis, and decelerate the progress of OA. Our research identifies the role of ASP in mitochondrial metabolism of OA chondrocytes through PPARγ/SOD2/ROS pathways, which provides a new idea for the treatment of OA.

Inactivation of Ras1 in Fission Yeast Aggravates the Oxidative Stress Response Induced by Tert Butyl Hydroperoxide (tBHP)

Ras proteins are small GTPases and function as molecular switches to regulate cellular homeostasis. Ras-dependent signalling pathways regulate several essential processes such as cell cycle progression, growth, migration, apoptosis, and senescence. The dysregulation of Ras signaling pathway has been linked to several pathological outcomes. A potential role of RAS in regulating the redox signalling pathway has been established that includes the manipulation of ROS levels to provide a redox milieu that might be conducive to carcinogenesis. Reactive oxygen species (ROS) and mitochondrial impairment have been proposed as major factors affecting the physiology of cells and implicated in several pathologies. The present study was conducted to evaluate the role of Ras1, tert Butyl hydroperoxide (tBHP), and antimycin A in oxidative stress response in Schizosaccharomyces pombe cells. We observed decreased cell survival, higher levels of ROS, and mitochondrial dysfunctionality in ras1Δ cells and tBHP as well as respiratory inhibitor, antimycin A treated wild type cells. Furthermore, these defects were more profound in ras1Δ cells treated with tBHP or antimycin A. Additionally, Ras1 also has been shown to regulate the expression and activity of several antioxidant enzymes like glutathione peroxidase (GSH-Px), glutathione-S-transferase (GST), and catalase. Together, these results suggest the potential role of S. pombe Ras1 in mitigating oxidative stress response.

Inactivation of Ras1 in Fission Yeast Aggravates the Oxidative Stress Response Induced by Tert Butyl Hydroperoxide (tBHP)

Inactivation of Ras1 in Fission Yeast Aggravates the Oxidative Stress Response Induced by Tert Butyl Hydroperoxide (tBHP)

Direct Tertiary Butyl Alcohol Formation via Catalytic Liquid Phase Isobutane Oxidation with Molecular Oxygen

A safe one-pot catalytic process for directly producing tertiary butyl alcohol (TBA) from liquid-phase isobutane oxidation with oxygen is demonstrated. This is achieved by operating outside the vapor phase flammability envelope and catalytically decomposing tertiary butyl hydroperoxide (TBHP), the main product of homogeneous isobutane oxidation, at 125 °C and 35 bar. Among a dozen heterogeneous metal-based catalysts tested, amorphous MnO2 (AMO) was found to be roughly an order of magnitude more active than supported Pd, Co, Au, and Nb-based catalysts for TBHP decomposition to TBA. As a result, high TBA/TBHP (up to 20.4) selectivity was achieved during isobutane oxidation in the presence of the AMO catalyst. The yield of gas phase C1 products was <1% and only a minor amount of acetone was produced as a β-scission byproduct. The use of n-hydroxy phthalimide (NHPI) as an initiator was found to enhance the TBA yield. This process provides a possible low energy pathway for making isobutylene from isobutane, avoiding the energy-intensive dehydrogenation and isobutane/isobutylene separation steps.

Iodine Catalysed Oxidative Cross‐Coupling of Thioureas and Amines without Desulfurization

AbstractIodine/tert‐butyl hydroperoxide (TBHP) mediated synthesis of sulfenamides via oxidative cross‐coupling of thioureas and amines without desulfurization is developed. Diversely substituted sulfenamides have been synthesized in moderate to good yields in short reaction time. The present strategy is further explored for the synthesis of functionalized thiazole derivatives. DFT studies and mechanistic investigations indicate that the current coupling reaction proceeds via radical pathway.

Plasma-assisted low-temperature oxidation of n-butane: A synchrotron photoionization mass spectrometry and kinetic modeling study

The chemical kinetics of plasma-assisted low-temperature oxidation of n-butane (n-C4H10, 340 K, 30 Torr) is investigated by synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS) and kinetic modeling. Species measurements are conducted in a flow reactor activated by a nanosecond discharge using SVUV-PIMS. Detailed species identification and quantification are reported in the present work. Fuel-specific oxygenated species including 2-butenal (2-C3H5CHO), methyl vinyl ketone (CH3COC2H3), butanone (CH3COC2H5), butanal (n-C3H7CHO), 2-methyloxetane (-CH(CH3)CH2CH2O-), 1,2-epoxybutane (-CH(C2H5)CH2O-), tetrahydrofuran (-CH2CH2CH2CH2O-), 1-/2-butanol (1-/2-C4H9OH), and butyl hydroperoxide (C4H9O2H) are detected. A kinetic model for n-C4H10 plasma is developed, which well predicts the mole fractions of most species observed in experiments. Kinetic modeling reveals that electron-impact reactions of n-C4H10 are the main sources for various C1-C4 alkenes, alkynes, and radicals. Therefore, these reactions have a significant effect on the fuel consumption pathways and species pool formation. Reactions involving alkyl peroxy (RO2), especially the self- and cross-reactions of RO2, are essential for RO2 depletion and the formation of alcohols, ketones, and aldehydes. On the other hand, the misprediction of the species detected in the system, such as C4 cyclic ethers, ethyl formate (HCOOC2H5), and acrolein (C2H3CHO), indicates that their formation pathways in the current mechanism are incompletely described. Further experimental and numerical research on these subjects is desired for the development of the kinetic models.

Inactivation of Ras1 in Fission Yeast Aggravates the Oxidative Stress Response Induced by Tert Butyl Hydroperoxide (tBHP)

Ras proteins are small GTPases and function as molecular switches to regulate cellular homeostasis. Ras-dependent signalling pathways regulate several essential processes such as cell cycle progression, growth, migration, apoptosis, and senescence. The dysregulation of Ras signaling pathway has been linked to several pathological outcomes. A potential role of RAS in regulating the redox signalling pathway has been established that includes the manipulation of ROS levels to provide a redox milieu that might be conducive to carcinogenesis. Reactive oxygen species (ROS) and mitochondrial impairment have been proposed as major factors affecting the physiology of cells and implicated in several pathologies. The present study was conducted to evaluate the role of Ras1, tert Butyl hydroperoxide (tBHP), and antimycin A in oxidative stress response in Schizosaccharomyces pombe cells. We observed decreased cell survival, higher levels of ROS, and mitochondrial dysfunctionality in ras1Δ cells and tBHP as well as respiratory inhibitor, antimycin A treated wild type cells. Furthermore, these defects were more profound in ras1Δ cells treated with tBHP or antimycin A. Additionally, Ras1 also has been shown to regulate the expression and activity of several antioxidant enzymes like glutathione peroxidase (GSH-Px), glutathione-S-transferase (GST), and catalase. Together, these results suggest the potential role of S. pombe Ras1 in mitigating oxidative stress response.

Zn(II)-catalysed enantioselective addition of alcohols and tert-butyl hydroperoxide to isatin-derived N-Boc ketimines.

Using binaphthyl-proline-based chiral ligands, Zn(II)-catalysed addition of alcohols and tert-butyl hydroperoxide to isatin-derived N-Boc ketimines provided the isatin-derived C3 N,O-aminals in up to 99% yield and up to 99% ee. The reactions could be carried out under mild conditions and a gram-scale reaction could be realized without the loss of the yield and enantioselectivity.

Аддукты арильных соединений сурьмы и висмута с карбоновыми кислотами, фенолами и оксимами

When the reaction products of triarylantimony or -bismuth with carboxylic acids, phenol, or oxime in the presence of tertiary butyl hydroperoxide (molar ratio 1:2:1, diethyl ether, 24 °C, 24 h) were recrystallized brom benzene or toluene, the adducts of antimony or bismuth aryl compounds with carboxylic acids, phenol, and oxime of the Ar3MX2 type were isolated as minor products. According to X-ray structural analysis performed at 293 K on a D8 Quest Bruker automatic four-circle diffractometer (two-coordinate CCD detector, Mo Kα radiation, λ = 0.71073 Å, graphite monochromator), metal atoms in crystals m-Tol3Sb[OC(O)C6H3F2-2,5]2 ∙ HOC(O)C6H3F2-2,5 (1) [C42H31O6F6Sb, M 867.42; triclinic syngony, symmetry group P1 ̅; cell parameters: a = 8.78(5), b = 13.10(6), c = 16.64(8) Å;  = 102.86(19), β = 99.3(2),  = 98.0(3) degrees; V = 1813(16) Å3; Z 2; reflection index intervals –7 ≤ h ≤ 7, –11 ≤ k ≤ 11, –14 ≤ l ≤ 14; total reflections 14149; independent reflections 2603; Rint 0.0284; GOOF 1.049; R1 = 0.0348, wR2 = 0.0938; residual electron density 0.55/0.42 e/Å3]; p-Tol3Bi[OC(O)C6HF4]2∙HOC(O)C6HF4 (2) [C42H25O6F12Bi, M 1062.60; triclinic syngony, symmetry group P1 ̅; cell parameters: a = 12.246(11), b = 12.976(18), c = 14.391(13) Å;  = 68.27(4), β = 69.89(3),  = 86.11(5) degrees; V = 1990(4) Å3; Z 2; reflection index intervals –15 ≤ h ≤ 15, –16 ≤ k ≤ 16, –18 ≤ l ≤ 18; total reflections 48542; independent reflections 9207; Rint 0.0321; GOOF 1,136; R1 = 0.0322, wR2 = 0.0648; residual electron density 1.81/1.08 e/Å3]; [(2-MeO-5-BrC6H3)3SbOC6H4Br-4]2O∙2HOC6H4Br-4 (3) [C66H54Br10O11Sb2, M 2065.69; monoclinic syngony, symmetry group C21/c; cell parameters: a = 12.017(14), b = 25.54(3), c = 13.181(18) Å; β = 116.71(5) degrees; V = 3613(8) Å3; Z 2; reflection index intervals –13 ≤ h ≤ 13, –27 ≤ k ≤ 27, –12 ≤ l ≤ 12; total reflections 29461; independent reflections 4545; Rint 0.0656; GOOF 1.062; R1 = 0.0565 wR2 = 0.1200; residual electron density 1.59/1.31 e/Å3]; [(2-MeO)C6H4]3Sb[ON=CHC4H2O(NO2-2)]2 ∙ 2HON=CHC4H2O(NO2-2) ∙ ½PhH (4) [C44H38N8O19Sb, M 1104.57; triclinic syngony, symmetry group P1 ̅; cell parameters: a = 10.240(5), b = 14.480(8), c = 18.093(11) Å;  = 103.43(3), β = 104.50(2),  = 98.876(17) degrees; V = 2461(2) Å3; Z 2; reflection index intervals –13 ≤ h ≤ 13, –18 ≤ k ≤ 18, –23 ≤ l ≤ 23; total reflections 58643; independent reflections 10886; Rint 0.0558; GOOF 1.061; R1 = 0.0429, wR2 = 0.1095; residual electron density 1.91/0.51 e/Å3] have a distorted trigonal-bipyramidal coordination with the oxygen atoms in axial positions. Complete tables of atomic coordinates, bond lengths, and bond angles for the structures were deposited at the Cambridge Crystallographic Data Center (no. 2050322 for 1, no. 2045173 for 2, no. 2070387 for 3, no. 2119790 for 4; deposit@ccdc.cam.ac.uk; https www.ccdc.cam.ac.uk).

Concepts of Heterogeneously Catalyzed Liquid‐Phase Oxidation of Cyclohexene with tert‐Butyl Hydroperoxide, Hydrogen Peroxide and Molecular Oxygen

AbstractThe oxidation of hydrocarbons is of great significance for the chemical industry as it provides access to valuable functionalized chemicals. The oxidation of cyclohexene has raised much interest because it enables the direct synthesis of adipic acid, which is an important building block in polymer chemistry. However, the selective oxidation of cyclohexene is rather challenging due to its two reactive centers so that epoxidation or allylic oxidation may occur leading to a variety of products. Whether the oxidation takes place at the allylic C−H bond or at the C=C bond is strongly influenced by the chosen oxidant and catalyst, and different reaction mechanisms can occur. Therefore, this concept article aims at giving a broad overview of the recent advances in the selective cyclohexene oxidation over heterogeneous transition metal‐based catalysts using environmentally benign oxidants like tert‐butyl hydroperoxide, H2O2 and molecular O2.

Reactive Human Plasma Glutathione Peroxidase Mutant with Diselenide Bond Succeeds in Tetramer Formation.

Plasma glutathione peroxidase (GPx3) belongs to the GPx superfamily, and it is the only known secreted selenocysteine (Sec)−containing GPx in humans. It exists as a glycosylated homotetramer and catalyzes the reduction of hydrogen peroxide and lipid peroxides, depending on the Sec in its active center. In this study, a previously reported chimeric tRNAUTuT6 was used for the incorporation of Sec at the UAG amber codon, and the mature form of human GPx3 (hGPx3) without the signal peptide was expressed in amber−less E. coli C321.ΔA.exp. Reactive Sec−hGPx3, able to reduce H2O2 and tert−butyl hydroperoxide (t−BuOOH), was produced with high purity and yield. Study of the quaternary structure suggested that the recombinant Sec−hGPx3 contained an intra−molecular disulfide bridge but failed to form tetramer. Mutational and structural analysis of the mutants with three Cys residues, individually or jointly replaced with Ser, indicated that the formation of intra−molecular disulfide bridges involved structure conformational changes. The secondary structure containing Cys77 and Cys132 was flexible and could form a disulfide bond, or form a sulfhydryl–selenyl bond with Sec49 in relative mutants. Mutation of Cys8 and Cys132 to Sec8 and Sec132 could fix the oligomerization loop through the formation of diselenide bond, which, in turn, facilitated tetramer formation and noticeably improved the GPx activity. This research provides an important foundation for the further catalysis and functional study of hGPx3.

Upregulation of osteoprotegerin inhibits tert-butyl hydroperoxide-induced apoptosis of human chondrocytes.

Necrosis of the femoral head (NFH) is an orthopedic disease characterized by a severe lack of blood supply to the femoral head and a marked increase in intraosseous pressure. NFH is associated with numerous factors, such as alcohol consumption and hormone levels. The present study focused on the expression levels of osteoprotegerin (OPG) in NFH and the effect of OPG overexpression on chondrocyte apoptosis. The results demonstrated that OPG expression was markedly decreased in the femoral head of patients with NFH compared with normal femoral heads. Lentivirus-mediated overexpression of OPG in human chondrocytes reversed the decrease in cell viability and the increase in reactive oxygen species production induced by an oxidative stress-inducing factor, tert-butyl hydroperoxide. Flow cytometry and TUNEL assays revealed that OPG overexpression inhibited the apoptosis of chondrocytes. In addition, it was revealed that OPG exerted its anti-apoptotic effect mainly by promoting Bcl-2 expression and Akt phosphorylation and inhibiting caspase-3 cleavage and Bax expression. The present study revealed that OPG may be an important regulator of NFH.

FEATURES OF KINETICS POLYMERIZATION OF METHYL METHACRYLATE INITIATED BY HYDROPEROXIDES -N, N-DIETHYLDITHIOCARBAMATES OF COPPER (II) SYSTEMS

Kinetic studies have shown that the use of systems based on secondary and tertiary hydroperoxides with N, N-diethyldithiocarbamate copper (II) can be used as effective sources of free radicals in the polymerization of methyl methacrylate in moderately low temperatures region (323–343 K). The introduction of an aromatic ring in molecules of hydroperoxides (ethylbenzene hydroperoxide and cumene hydroperoxide) increases the reactivity of the initiating system «hydroperoxide – complex» in comparison with tertiary butyl hydroperoxide. The shift of the gel effect to the region of high conversions during the polymerization of methyl methacrylate was noted. Such systems allow not only to accelerate the polymerization of the monomer, but also to conduct it in a controlled mode. H1 NMR spectroscopy showed that the formed polymers contained end dithiocarbamate fragments. Such groups are labile. It has been shown that the obtained and isolated in the presence of the initiating system tertiary hydroperoxide – N,N-diethyldithiocarbamate of copper(II) polymers are macroinitiators that can initiate a new portion of the monomer.

Accounting for molecular flexibility in photoionization: case of tert-butyl hydroperoxide.

tert-Butyl hydroperoxide (tBuOOH) is a common intermediate in the oxidation of organic compounds that needs to be accurately quantified in complex gas mixtures for the development of chemical kinetic models of low temperature combustion. This work presents a combined theoretical and experimental investigation on the synchrotron-based VUV single photon ionization of gas-phase tBuOOH in the 9.0 - 11.0 eV energy range, including dissociative ionization processes. Computations consist of the determination of the structures, vibrational frequencies and the energetics of neutral and ionic tBuOOH. The Franck-Condon spectrum for the tBuOOH+ (X+) + e- ← tBuOOH (X) + hν transition is computed, where special treatment is undertaken because of the flexibility of tBuOOH, in particular regarding the OOH group. Through comparison of the experimental mass-selected threshold photoelectron spectra with explicitly correlated coupled cluster calculations and Franck-Condon simulations that account for the flexibility of the molecule, an estimation of the ionization energy is given. The appearance energy of the only fragment observed within the above-mentioned energy range, identified as the tert-butyl C4H9+, is also reported. Finally, the signal branching ratio between the parent and the fragment ions is provided as a function of photon energy, essential to quantify tBuOOH in gas-phase oxidation/combustion experiments via advanced mass spectrometry techniques.